Signal Limit Based On Detecting Clipping

Abstract

Example techniques may involve controlling a passive radiator. An implementation may include a device receiving, via a network interface, audio content and generating an audio signal representing the audio content. Generating the audio signal involves modifying portions of the audio content to limit excursion of the speaker driver to less than an excursion limit when a forward prediction model indicates that the portions of the audio content are predicted to cause the speaker driver to move beyond the excursion limit. While playing back the generated audio signal via the audio stage, the device detects, via a sensor, clipping of the speaker driver and generates a feedback signal based on the detected clipping of the speaker driver. The device adjusts the forward prediction model based on the generated feedback signal.

We claim: 
     
         1 . A playback device comprising:
 a sealed enclosure;   an audio system carried by the sealed enclosure, wherein the audio system comprises an amplifier, a voice coil, a magnet assembly, and a moveable surface, wherein movement of the voice coil in response to electrical signals received via the amplifier causes corresponding movement of the moveable surface within an excursion range;   an input interface;   at least one sensor;   
       at least one processor; and 
       at least one non-transitory computer-readable medium comprising program instructions that are executable by the at least one processor such that the playback device is configured to:
 receive, via the input interface, data representing audio content; 
 predict, based on the received data and a transducer model, that playback of the audio content via the amplifier and the voice coil will cause the moveable surface to exceed an excursion limit of the excursion range; 
 modify, based on the transducer model, portions of the audio content to limit excursion of the moveable surface to less than the excursion limit; 
 play back the modified audio content via the amplifier and the voice coil; 
 during playback of the modified audio content, determine, via the at least one sensor, one or more positions of at least one of the moveable surface and the voice coil; 
 generate a feedback signal based on the one or more determined positions; and 
 adjust the transducer model based on the generated feedback signal. 
 
     
     
         2 . The playback device of  claim 1 , wherein the at least one sensor comprises a position sensor that is carried in a fixed position within the sealed enclosure. 
     
     
         3 . The playback device of  claim 2 , wherein the instructions that are executable by the at least one processor such that the playback device is configured to determine the one or more positions of at least one of the moveable surface and the voice coil comprise instructions that are executable by the at least one processor such that the playback device is configured to:
 while the moveable surface is moving, measure, via the at least one sensor, positions of the moveable surface relative to the fixed position.   
     
     
         4 . The playback device of  claim 2 , wherein the instructions that are executable by the at least one processor such that the playback device is configured to determine the one or more positions of at least one of the moveable surface and the voice coil comprise instructions that are executable by the at least one processor such that the playback device is configured to:
 while the voice coil is moving, measure, via the at least one sensor, positions of the voice coil relative to the fixed position.   
     
     
         5 . The playback device of  claim 2 , wherein the position sensor comprises a capacitive sensor configured to measure capacitance between the capacitive sensor and at least one of the moveable surface and the voice coil, wherein changes in capacitance indicate the one or more positions of at least one of the moveable surface and the voice coil. 
     
     
         6 . The playback device of  claim 1 , wherein the at least one sensor is moveable with movement of at least one of the moveable surface and the voice coil, and wherein the instructions that are executable by the at least one processor such that the playback device is configured to determine the one or more positions of at least one of the moveable surface and the voice coil comprise instructions that are executable by the at least one processor such that the playback device is configured to:
 while the moveable surface and the voice coil are moving, measure, via the at least one sensor, positions of the voice coil relative to a fixed position within the sealed enclosure.   
     
     
         7 . The playback device of  claim 1 , wherein the instructions that are executable by the at least one processor such that the playback device is configured to generate the feedback signal comprise instructions that are executable by the at least one processor such that the playback device is configured to:
 generate a particular feedback signal representing differences between the determined one or more positions and excursion predicted by the received data and the transducer model.   
     
     
         8 . The playback device of  claim 7 , wherein the instructions that are executable by the at least one processor such that the playback device is configured to adjust the transducer model comprise instructions that are executable by the at least one processor such that the playback device is configured to:
 adjust the transducer model to offset differences between the determined one or more positions and the excursion predicted by the received data and the transducer model.   
     
     
         9 . The playback device of  claim 1 , wherein the instructions are executable by the at least one processor such that the playback device is further configured to:
 buffer the received audio content to delay playback of the received audio content by a particular delay.   
     
     
         10 . The playback device of  claim 1 , wherein the audio system further comprises an additional voice coil, an additional magnet assembly, and an additional moveable surface, wherein movement of the additional voice coil in response to electrical signals received via the amplifier causes corresponding movement of the additional moveable surface within an additional excursion range, and wherein the instructions are executable by the at least one processor such that the playback device is further configured to:
 predict, based on the received data and an additional transducer model, that playback of the audio content via the amplifier and the additional voice coil will cause the additional moveable surface to exceed an excursion limit of the excursion range;   modify, based on the addition transducer model, additional portions of the audio content to limit excursion of the additional moveable surface to less than the excursion limit;   play back the modified audio content via the amplifier and the additional voice coil;   during playback of the modified audio content, determine, via the at least one sensor, one or more positions of at least one of the additional moveable surface and the additional voice coil;   generate an additional feedback signal based on the one or more determined positions; and   adjust the additional transducer model based on the generated additional feedback signal.   
     
     
         11 . A system comprising:
 a playback device comprising a sealed enclosure and an audio system carried by the sealed enclosure, wherein the audio system comprises an amplifier, a voice coil, a magnet assembly, and a moveable surface, wherein movement of the voice coil in response to electrical signals received via the amplifier causes corresponding movement of the moveable surface within an excursion range;   an input interface;   at least one sensor;   
       at least one processor; and 
       at least one non-transitory computer-readable medium comprising program instructions that are executable by the at least one processor such that the system is configured to:
 receive, via the input interface, data representing audio content; 
 predict, based on the received data and a transducer model, that playback of the audio content via the amplifier and the voice coil will cause the moveable surface to exceed an excursion limit of the excursion range; 
 modify, based on the transducer model, portions of the audio content to limit excursion of the moveable surface to less than the excursion limit; 
 play back the modified audio content via the amplifier and the voice coil; 
 during playback of the modified audio content, determine, via the at least one sensor, one or more positions of at least one of the moveable surface and the voice coil; 
 generate a feedback signal based on the one or more determined positions; and 
 adjust the transducer model based on the generated feedback signal. 
 
     
     
         12 . The system of  claim 11 , wherein the at least one sensor comprises a position sensor that is carried in a fixed position within the sealed enclosure. 
     
     
         13 . The system of  claim 12 , wherein the instructions that are executable by the at least one processor such that the system is configured to determine the one or more positions of at least one of the moveable surface and the voice coil comprise instructions that are executable by the at least one processor such that the system is configured to:
 while the moveable surface is moving, measure, via the at least one sensor, positions of the moveable surface relative to the fixed position.   
     
     
         14 . The system of  claim 12 , wherein the instructions that are executable by the at least one processor such that the system is configured to determine the one or more positions of at least one of the moveable surface and the voice coil comprise instructions that are executable by the at least one processor such that the system is configured to:
 while the voice coil is moving, measure, via the at least one sensor, positions of the voice coil relative to the fixed position.   
     
     
         15 . The system of  claim 12 , wherein the position sensor comprises a capacitive sensor configured to measure capacitance between the capacitive sensor and at least one of the moveable surface and the voice coil, wherein changes in capacitance indicate the one or more positions of at least one of the moveable surface and the voice coil. 
     
     
         16 . The system of  claim 11 , wherein the at least one sensor is moveable with movement of at least one of the moveable surface and the voice coil, and wherein the instructions that are executable by the at least one processor such that the system is configured to determine the one or more positions of at least one of the moveable surface and the voice coil comprise instructions that are executable by the at least one processor such that the system is configured to:
 while the moveable surface and the voice coil are moving, measure, via the at least one sensor, positions of the voice coil relative to a fixed position within the sealed enclosure.   
     
     
         17 . The system of  claim 11 , wherein the instructions that are executable by the at least one processor such that the system is configured to generate the feedback signal comprise instructions that are executable by the at least one processor such that the system is configured to:
 generate a particular feedback signal representing differences between the determined one or more positions and excursion predicted by the received data and the transducer model.   
     
     
         18 . The system of  claim 17 , wherein the instructions that are executable by the at least one processor such that the system is configured to adjust the transducer model comprise instructions that are executable by the at least one processor such that the system is configured to:
 adjust the transducer model to offset differences between the determined one or more positions and the excursion predicted by the received data and the transducer model.   
     
     
         19 . The system of  claim 11 , wherein the instructions are executable by the at least one processor such that the system is further configured to:
 buffer the received audio content to delay playback of the received audio content by a particular delay.   
     
     
         20 . At least one non-transitory computer-readable medium comprising program instructions that are executable by at least one processor such that a playback device is configured to:
 receive, via an input interface, data representing audio content, wherein the playback device comprises: a sealed enclosure and an audio system carried by the sealed enclosure, wherein the audio system comprises an amplifier, a voice coil, a magnet assembly, and a moveable surface, wherein movement of the voice coil in response to electrical signals received via the amplifier causes corresponding movement of the moveable surface within an excursion range;   predict, based on the received data and a transducer model, that playback of the audio content via the amplifier and the voice coil will cause the moveable surface to exceed an excursion limit of the excursion range;   modify, based on the transducer model, portions of the audio content to limit excursion of the moveable surface to less than the excursion limit;   play back the modified audio content via the amplifier and the voice coil;   during playback of the modified audio content, determine, via at least one sensor, one or more positions of at least one of the moveable surface and the voice coil;   generate a feedback signal based on the one or more determined positions; and   adjust the transducer model based on the generated feedback signal.